Stroke?

From what I've been able to read the best prevention for strokes is to try and stay healthy (avoid smoking, overly large amounts of alcohol consumption, high cholesterol, etc) . Prevention for people who have already had strokes is to generally talk with a doctor about the issue and see what is recommended.

However, if you're worried about hurting him, there doesn't appear to be much evidence in what I can find that suggests any likelihood you could. Just watch him and make sure he's keeping healthy.

What type of stroke did he have?

Strokes can happen for many different reasons, so is like asking that he had an accident and if there is anything you can do about it. There are many types of accidents we all can have.